This invention relates to a structure for use in an internal combustion engine for transmitting, with minimized attenuation, vibrations due to internal combustion in engine cylinders to a knock sensor attached to the engine at an exterior location.
It is the common practice to improve fuel economy in an internal combustion engine by advancing the spark of the engine as close as possible to a value above which knocking occurs and by retarding the spark immediately when knocking occurs. For this purpose, spark control circuits have been proposed which can advance and retard the spark of an engine in response to the frequency of occurrence of engine knock. Such a spark control circuit includes a knock sensor attached to an engine at an exterior location where vibratory forces within the engine are translated into voltage signals at the knock sensor output. The spark control circuit also includes a pulse generator connected to the knock sensor for generating pulses to a counter while the knock sensor output is greater than the signal of background vibration produced by normal engine operation without knocking. The count of the counter corresponds to the frequency of occurrence of engine knock.
Accordingly, the need has been recognized for a new and improved structure capable of transmitting vibrations due to internal combustion in engine cylinders to the knock sensor with minimized attenuation and minimized distortion.